Comment 56 for bug 164640

(In reply to comment #6)
> I'll let Keith pronounce if this is feasible. Possibilities I see:
> * reparse the configuration file after the constants have been registered (not
> sure fontconfig allows this, not so nice for performance).
> * introduce a cairo_init() method that cairo consumers have to call before
> touching fontconfig (adds burden/incompatibility to cairo users).
>
> Otherwise, there is a third possibility: Keep this parameter in fontconfig and
> change cairo to take it into account, as this is done for antialiasing,
> subpixel order or hinting.
>
> I'm questioning having such an option at all, see
> http://lists.cairographics.org/archives/cairo/2008-January/012685.html

While I personally agree that the "Default" filter is adequate, we still need to have at least the "Legacy" filter available. The loss of this more-known, thinner filter would probably cause outrage among those who consider the new filters "too blurry."
In that regard, I think that having "Default" as the default, but having only Xrdb configuration to set the other filters would be sufficient.